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Caesar cipher

Caesar cipher, is one of the simplest and most widely known encryption techniques. The transformation can be represented by aligning two alphabets, the cipher alphabet is the plain alphabet rotated left or right by some number of positions.

When encrypting, a person looks up each letter of the message in the 'plain' line and writes down the corresponding letter in the 'cipher' line. Deciphering is done in reverse.
The encryption can also be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,..., Z = 25. Encryption of a letter x by a shift n can be described mathematically as

Plaintext: ebonys
cipher variations:
fcpozt gdqpau herqbv ifsrcw jgtsdx
khutey livufz mjwvga nkxwhb olyxic
pmzyjd qnazke robalf spcbmg tqdcnh
uredoi vsfepj wtgfqk xuhgrl yvihsm
zwjitn axkjuo bylkvp czmlwq danmxr

Decryption is performed similarly,

(There are different definitions for the modulo operation. In the above, the result is in the range 0...25. I.e., if x+n or x-n are not in the range 0...25, we have to subtract or add 26.)
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Atbash Cipher

Atbash is an ancient encryption system created in the Middle East. It was originally used in the Hebrew language.
The Atbash cipher is a simple substitution cipher that relies on transposing all the letters in the alphabet such that the resulting alphabet is backwards.
The first letter is replaced with the last letter, the second with the second-last, and so on.
An example plaintext to ciphertext using Atbash:
Plain: ebonys
Cipher: vylmbh

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Baconian Cipher

To encode a message, each letter of the plaintext is replaced by a group of five of the letters 'A' or 'B'. This replacement is done according to the alphabet of the Baconian cipher, shown below.
a   AAAAA   g    AABBA     m    ABABB   s    BAAAB     y    BABBA
b   AAAAB   h    AABBB     n    ABBAA   t    BAABA     z    BABBB
c   AAABA   i    ABAAA     o    ABBAB   u    BAABB 
d   AAABB   j    BBBAA     p    ABBBA   v    BBBAB
e   AABAA   k    ABAAB     q    ABBBB   w    BABAA
f   AABAB   l    ABABA     r    BAAAA   x    BABAB

Plain: ebonys

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Affine Cipher
In the affine cipher the letters of an alphabet of size m are first mapped to the integers in the range 0..m - 1. It then uses modular arithmetic to transform the integer that each plaintext letter corresponds to into another integer that correspond to a ciphertext letter. The encryption function for a single letter is

where modulus m is the size of the alphabet and a and b are the key of the cipher. The value a must be chosen such that a and m are coprime.
Considering the specific case of encrypting messages in English (i.e. m = 26), there are a total of 286 non-trivial affine ciphers, not counting the 26 trivial Caesar ciphers. This number comes from the fact there are 12 numbers that are coprime with 26 that are less than 26 (these are the possible values of a). Each value of a can have 26 different addition shifts (the b value) ; therefore, there are 12*26 or 312 possible keys.
Plaintext: ebonys
cipher variations:

The decryption function is

where a - 1 is the modular multiplicative inverse of a modulo m. I.e., it satisfies the equation

The multiplicative inverse of a only exists if a and m are coprime. Hence without the restriction on a decryption might not be possible. It can be shown as follows that decryption function is the inverse of the encryption function,

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ROT13 Cipher
Applying ROT13 to a piece of text merely requires examining its alphabetic characters and replacing each one by the letter 13 places further along in the alphabet, wrapping back to the beginning if necessary. A becomes N, B becomes O, and so on up to M, which becomes Z, then the sequence continues at the beginning of the alphabet: N becomes A, O becomes B, and so on to Z, which becomes M. Only those letters which occur in the English alphabet are affected; numbers, symbols, whitespace, and all other characters are left unchanged. Because there are 26 letters in the English alphabet and 26 = 2 * 13, the ROT13 function is its own inverse:

ROT13(ROT13(x)) = x for any basic Latin-alphabet text x

An example plaintext to ciphertext using ROT13:

Plain: ebonys
Cipher: robalf

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Polybius Square

A Polybius Square is a table that allows someone to translate letters into numbers. To give a small level of encryption, this table can be randomized and shared with the recipient. In order to fit the 26 letters of the alphabet into the 25 spots created by the table, the letters i and j are usually combined.
1 2 3 4 5
1 A B C D E
2 F G H I/J K
3 L M N O P
4 Q R S T U
5 V W X Y Z

Basic Form:
Plain: ebonys
Cipher: 512143334534

Extended Methods:
Method #1

Plaintext: ebonys
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
e b o n y s 
5 2 4 3 4 3 
1 1 3 3 5 4 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: ebonys
Cipher: kooanu

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Method #3

Plaintext: ebonys
method variations:
fqnspy qnspyf nspyfq
spyfqn pyfqns yfqnsp

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Permutation Cipher
In classical cryptography, a permutation cipher is a transposition cipher in which the key is a permutation. To apply a cipher, a random permutation of size E is generated (the larger the value of E the more secure the cipher). The plaintext is then broken into segments of size E and the letters within that segment are permuted according to this key.
In theory, any transposition cipher can be viewed as a permutation cipher where E is equal to the length of the plaintext; this is too cumbersome a generalisation to use in actual practice, however.
The idea behind a permutation cipher is to keep the plaintext characters unchanged, butalter their positions by rearrangement using a permutation
This cipher is defined as:
Let m be a positive integer, and K consist of all permutations of {1,...,m}
For a key (permutation) , define:
The encryption function
The decryption function
A small example, assuming m = 6, and the key is the permutation :

The first row is the value of i, and the second row is the corresponding value of (i)
The inverse permutation, is constructed by interchanging the two rows, andrearranging the columns so that the first row is in increasing order, Therefore, is:

Total variation formula:

e = 2,718281828 , n - plaintext length

Plaintext: ebonys

all 720 cipher variations:
ebonys ebonsy eboyns eboysn ebosyn ebosny ebnoys ebnosy ebnyos ebnyso ebnsyo
ebnsoy ebynos ebynso ebyons ebyosn ebyson ebysno ebsnyo ebsnoy ebsyno ebsyon
ebsoyn ebsony eobnys eobnsy eobyns eobysn eobsyn eobsny eonbys eonbsy eonybs
eonysb eonsyb eonsby eoynbs eoynsb eoybns eoybsn eoysbn eoysnb eosnyb eosnby
eosynb eosybn eosbyn eosbny enobys enobsy enoybs enoysb enosyb enosby enboys
enbosy enbyos enbyso enbsyo enbsoy enybos enybso enyobs enyosb enysob enysbo
ensbyo ensboy ensybo ensyob ensoyb ensoby eyonbs eyonsb eyobns eyobsn eyosbn
eyosnb eynobs eynosb eynbos eynbso eynsbo eynsob eybnos eybnso eybons eybosn
eybson eybsno eysnbo eysnob eysbno eysbon eysobn eysonb esonyb esonby esoynb
esoybn esobyn esobny esnoyb esnoby esnyob esnybo esnbyo esnboy esynob esynbo
esyonb esyobn esybon esybno esbnyo esbnoy esbyno esbyon esboyn esbony beonys
beonsy beoyns beoysn beosyn beosny benoys benosy benyos benyso bensyo bensoy
beynos beynso beyons beyosn beyson beysno besnyo besnoy besyno besyon besoyn
besony boenys boensy boeyns boeysn boesyn boesny boneys bonesy bonyes bonyse
bonsye bonsey boynes boynse boyens boyesn boysen boysne bosnye bosney bosyne
bosyen boseyn boseny bnoeys bnoesy bnoyes bnoyse bnosye bnosey bneoys bneosy
bneyos bneyso bnesyo bnesoy bnyeos bnyeso bnyoes bnyose bnysoe bnyseo bnseyo
bnseoy bnsyeo bnsyoe bnsoye bnsoey byones byonse byoens byoesn byosen byosne
bynoes bynose byneos byneso bynseo bynsoe byenos byenso byeons byeosn byeson
byesno bysneo bysnoe byseno byseon bysoen bysone bsonye bsoney bsoyne bsoyen
bsoeyn bsoeny bsnoye bsnoey bsnyoe bsnyeo bsneyo bsneoy bsynoe bsyneo bsyone
bsyoen bsyeon bsyeno bsenyo bsenoy bseyno bseyon bseoyn bseony obenys obensy
obeyns obeysn obesyn obesny obneys obnesy obnyes obnyse obnsye obnsey obynes
obynse obyens obyesn obysen obysne obsnye obsney obsyne obsyen obseyn obseny
oebnys oebnsy oebyns oebysn oebsyn oebsny oenbys oenbsy oenybs oenysb oensyb
oensby oeynbs oeynsb oeybns oeybsn oeysbn oeysnb oesnyb oesnby oesynb oesybn
oesbyn oesbny onebys onebsy oneybs oneysb onesyb onesby onbeys onbesy onbyes
onbyse onbsye onbsey onybes onybse onyebs onyesb onyseb onysbe onsbye onsbey
onsybe onsyeb onseyb onseby oyenbs oyensb oyebns oyebsn oyesbn oyesnb oynebs
oynesb oynbes oynbse oynsbe oynseb oybnes oybnse oybens oybesn oybsen oybsne
oysnbe oysneb oysbne oysben oysebn oysenb osenyb osenby oseynb oseybn osebyn
osebny osneyb osneby osnyeb osnybe osnbye osnbey osyneb osynbe osyenb osyebn
osyben osybne osbnye osbney osbyne osbyen osbeyn osbeny nboeys nboesy nboyes
nboyse nbosye nbosey nbeoys nbeosy nbeyos nbeyso nbesyo nbesoy nbyeos nbyeso
nbyoes nbyose nbysoe nbyseo nbseyo nbseoy nbsyeo nbsyoe nbsoye nbsoey nobeys
nobesy nobyes nobyse nobsye nobsey noebys noebsy noeybs noeysb noesyb noesby
noyebs noyesb noybes noybse noysbe noyseb noseyb noseby nosyeb nosybe nosbye
nosbey neobys neobsy neoybs neoysb neosyb neosby neboys nebosy nebyos nebyso
nebsyo nebsoy neybos neybso neyobs neyosb neysob neysbo nesbyo nesboy nesybo
nesyob nesoyb nesoby nyoebs nyoesb nyobes nyobse nyosbe nyoseb nyeobs nyeosb
nyebos nyebso nyesbo nyesob nybeos nybeso nyboes nybose nybsoe nybseo nysebo
nyseob nysbeo nysboe nysobe nysoeb nsoeyb nsoeby nsoyeb nsoybe nsobye nsobey
nseoyb nseoby nseyob nseybo nsebyo nseboy nsyeob nsyebo nsyoeb nsyobe nsyboe
nsybeo nsbeyo nsbeoy nsbyeo nsbyoe nsboye nsboey ybones ybonse yboens yboesn
ybosen ybosne ybnoes ybnose ybneos ybneso ybnseo ybnsoe ybenos ybenso ybeons
ybeosn ybeson ybesno ybsneo ybsnoe ybseno ybseon ybsoen ybsone yobnes yobnse
yobens yobesn yobsen yobsne yonbes yonbse yonebs yonesb yonseb yonsbe yoenbs
yoensb yoebns yoebsn yoesbn yoesnb yosneb yosnbe yosenb yosebn yosben yosbne
ynobes ynobse ynoebs ynoesb ynoseb ynosbe ynboes ynbose ynbeos ynbeso ynbseo
ynbsoe ynebos ynebso yneobs yneosb ynesob ynesbo ynsbeo ynsboe ynsebo ynseob
ynsoeb ynsobe yeonbs yeonsb yeobns yeobsn yeosbn yeosnb yenobs yenosb yenbos
yenbso yensbo yensob yebnos yebnso yebons yebosn yebson yebsno yesnbo yesnob
yesbno yesbon yesobn yesonb ysoneb ysonbe ysoenb ysoebn ysoben ysobne ysnoeb
ysnobe ysneob ysnebo ysnbeo ysnboe ysenob ysenbo yseonb yseobn ysebon ysebno
ysbneo ysbnoe ysbeno ysbeon ysboen ysbone sbonye sboney sboyne sboyen sboeyn
sboeny sbnoye sbnoey sbnyoe sbnyeo sbneyo sbneoy sbynoe sbyneo sbyone sbyoen
sbyeon sbyeno sbenyo sbenoy sbeyno sbeyon sbeoyn sbeony sobnye sobney sobyne
sobyen sobeyn sobeny sonbye sonbey sonybe sonyeb soneyb soneby soynbe soyneb
soybne soyben soyebn soyenb soenyb soenby soeynb soeybn soebyn soebny snobye
snobey snoybe snoyeb snoeyb snoeby snboye snboey snbyoe snbyeo snbeyo snbeoy
snyboe snybeo snyobe snyoeb snyeob snyebo snebyo sneboy sneybo sneyob sneoyb
sneoby syonbe syoneb syobne syoben syoebn syoenb synobe synoeb synboe synbeo
synebo syneob sybnoe sybneo sybone syboen sybeon sybeno syenbo syenob syebno
syebon syeobn syeonb seonyb seonby seoynb seoybn seobyn seobny senoyb senoby
senyob senybo senbyo senboy seynob seynbo seyonb seyobn seybon seybno sebnyo
sebnoy sebyno sebyon seboyn sebony

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History of cryptography
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